Morphological Control of Self‐Assembled Monolayers on Multiple‐Solvent‐Doped PEDOT:PSS Electrodes for Ultrathin Flexible Organic Optoelectronics

ABSTRACT Ultrathin flexible organic optoelectronic devices are widely used in wearable electronics applications due to their advantages of thickness, flexibility, conformable adherence, and low cost. In recent years, self‐assembled monolayers (SAMs) have garnered considerable attention in the fabrication of high‐performance organic optoelectronics. However, most of the existing studies focus on investigating the optimization of SAMs on the rigid ITO electrode, while there is still a lack of systematic studies on their morphological evolution and anchoring mechanism on the surface of the flexible transparent electrode. In this work, high‐quality PEDOT:PSS electrodes are developed through a multiple‐solvent doping strategy, followed by the modification of SAMs to tune their work function. High efficiency charge transport and collection are achieved by using the SAMs modified PEDOT:PSSelectrodes. The ultrathin flexible organic solar cells (OSCs) based on this flexible electrode achieve a power conversion efficiency (PCE) of 15.2%. All‐solution‐processed ultrathin flexible OSCs and organic photodetectors are also fabricated with liquid metal EGaIn top electrodes. The OSCs achieve a surprising PCE of 14.6%, and the OPDs are being used for real‐time photoplethysmograph (PPG) sensing with excellent sensitivity. This work paves the way for the advancement of next‐generation ultrathin flexible electronics.